RE: I thought this was a substitute for Tumblr that had NSFW content
Cheers for posting. At this moment we don't really "promote" sites from users in a central location. There is a link on the front page which shows recent images & likes from selected user sites.
I would suggest you do a bit of searching for sites you like. And if you can't find one, or there isn't one available, just start one yourself.
The project is quite new and can't have all kinds of content from the start